Die processing

ABSTRACT

Representative implementations provide techniques and systems for processing integrated circuit (IC) dies. Dies being prepared for intimate surface bonding (to other dies, to substrates, to another surface, etc.) may be processed with a minimum of handling, to prevent contamination of the surfaces or the edges of the dies. The techniques include processing dies while the dies are on a dicing sheet or other device processing film or surface. Systems include integrated cleaning components arranged to perform multiple cleaning processes simultaneously.

PRIORITY CLAIM AND CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims the benefit of priorityunder 35 U.S.C. § 120 from U.S. patent application Ser. No. 17/231,965,filed Apr. 15, 2021, which is a continuation of U.S. patent applicationSer. No. 16/910,432, filed Jun. 24, 2020, now U.S. Pat. No. 10,985,133,issued Apr. 20, 2021, which is a continuation of U.S. patent applicationSer. No. 16/515,588, filed Jul. 18, 2019, now U.S. Pat. No. 10,714,449,issued Jul. 14, 2020, which is a continuation of and claims the benefitof priority under 35 U.S.C. § 120 from U.S. patent application Ser. No.16/282,024, filed Feb. 21, 2019, now U.S. Pat. No. 10,515,925, issuedDec. 24, 2019, which is a continuation of U.S. patent application Ser.No. 15/936,075, filed Mar. 26, 2018, now U.S. Pat. No. 10,269,756,issued Apr. 23, 2019, which claims the benefit of priority to U.S.Provisional Patent Application No. 62/563,847, filed Sep. 27, 2017, andU.S. Provisional Patent Application No. 62/488,340, filed Apr. 21, 2017,which are hereby incorporated by reference in their entirety.

FIELD

The following description relates to processing of integrated circuits(“ICs”). More particularly, the following description relates to devicesand techniques for processing IC dies.

BACKGROUND

The demand for more compact physical arrangements of microelectronicelements such as integrated chips and dies has become even more intensewith the rapid progress of portable electronic devices, the expansion ofthe Internet of Things, nano-scale integration, subwavelength opticalintegration, and more. Merely by way of example, devices commonlyreferred to as “smart phones” integrate the functions of a cellulartelephone with powerful data processors, memory and ancillary devicessuch as global positioning system receivers, electronic cameras, andlocal area network connections along with high-resolution displays andassociated image processing chips. Such devices can provide capabilitiessuch as full internet connectivity, entertainment includingfull-resolution video, navigation, electronic banking, sensors,memories, microprocessors, healthcare electronics, automaticelectronics, and more, all in a pocket-size device. Complex portabledevices require packing numerous chips and dies into a small space.

Microelectronic elements often comprise a thin slab of a semiconductormaterial, such as silicon or gallium arsenide or others. Chips and diesare commonly provided as individual, prepackaged units. In some unitdesigns, the die is mounted to a substrate or a chip carrier, which isin turn mounted on a circuit panel, such as a printed circuit board(PCB). Dies can be provided in packages that facilitate handling of thedie during manufacture and during mounting of the die on the externalsubstrate. For example, many dies are provided in packages suitable forsurface mounting. Numerous packages of this general type have beenproposed for various applications. Most commonly, such packages includea dielectric element, commonly referred to as a “chip carrier” withterminals formed as plated or etched metallic structures on thedielectric. The terminals typically are connected to the contacts (e.g.,bond pads or metal posts) of the die by conductive features such as thintraces extending along the die carrier and by fine leads or wiresextending between the contacts of the die and the terminals or traces.In a surface mounting operation, the package may be placed onto acircuit board so that each terminal on the package is aligned with acorresponding contact pad on the circuit board. Solder or other bondingmaterial is generally provided between the terminals and the contactpads. The package can be permanently bonded in place by heating theassembly so as to melt or “reflow” the solder or otherwise activate thebonding material.

Many packages include solder masses in the form of solder balls that aretypically between about 0.025 mm and about 0.8 mm (1 and 30 mils) indiameter, and are attached to the terminals of the package. A packagehaving an array of solder balls projecting from its bottom surface(e.g., surface opposite the front face of the die) is commonly referredto as a ball grid array or “BGA” package. Other packages, referred to asland grid array or “LGA” packages are secured to the substrate by thinlayers or lands formed from solder. Packages of this type can be quitecompact. Certain packages, commonly referred to as “chip scalepackages,” occupy an area of the circuit board equal to, or onlyslightly larger than, the area of the device incorporated in thepackage. This scale is advantageous in that it reduces the overall sizeof the assembly and permits the use of short interconnections betweenvarious devices on the substrate, which in turn limits signalpropagation time between devices and thus facilitates operation of theassembly at high speeds.

Semiconductor dies can also be provided in “stacked” arrangements,wherein one die is provided on a carrier, for example, and another dieis mounted on top of the first die. These arrangements can allow anumber of different dies to be mounted within a single footprint on acircuit board and can further facilitate high-speed operation byproviding a short interconnection between the dies. Often, thisinterconnect distance can be only slightly larger than the thickness ofthe die itself. For interconnection to be achieved within a stack of diepackages, interconnection structures for mechanical and electricalconnection may be provided on both sides (e.g., faces) of each diepackage (except for the topmost package). This has been done, forexample, by providing contact pads or lands on both sides of thesubstrate to which the die is mounted, the pads being connected throughthe substrate by conductive vias or the like. Examples of stacked chiparrangements and interconnect structures are provided in U.S. PatentApp. Pub. No. 2010/0232129, the disclosure of which is incorporated byreference herein.

Dies or wafers may also be stacked in other three-dimensionalarrangements as part of various microelectronic packaging schemes. Thiscan include stacking layers of one or more dies or wafers on a largerbase die or wafer, stacking multiple dies or wafers in vertical orhorizontal arrangements, or stacking similar or dissimilar substrates,where one or more of the substrates may contain electrical ornon-electrical elements, optical or mechanical elements, and/or variouscombinations of these. Dies or wafers may be bonded in a stackedarrangement using various bonding techniques, including directdielectric bonding, non-adhesive techniques, such as ZiBond® or a hybridbonding technique, such as DBI®, both available from Invensas BondingTechnologies, Inc. (formerly Ziptronix, Inc.), an Xperi company (see forexample, U.S. Pat. Nos. 6,864,585 and 7,485,968, which are incorporatedherein in their entirety). When bonding stacked dies using a directbonding technique, it is usually desirable that the surfaces of the diesto be bonded be extremely flat and smooth. For instance, in general, thesurfaces should have a very low variance in surface topology, so thatthe surfaces can be closely mated to form a lasting bond. For example,it is generally preferable that the variation in roughness of thebonding surfaces be less than 3 nm and preferably less than 1.0 nm.

Some stacked die arrangements are sensitive to the presence of particlesor contamination on one or both surfaces of the stacked dies. Forinstance, particles remaining from processing steps or contaminationfrom die processing or tools can result in poorly bonded regions betweenthe stacked dies, or the like. Extra handling steps during dieprocessing can further exacerbate the problem, leaving behind unwantedresidues.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is set forth with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference numbers in different figures indicates similaror identical items.

For this discussion, the devices and systems illustrated in the figuresare shown as having a multiplicity of components. Variousimplementations of devices and/or systems, as described herein, mayinclude fewer components and remain within the scope of the disclosure.Alternately, other implementations of devices and/or systems may includeadditional components, or various combinations of the describedcomponents, and remain within the scope of the disclosure.

FIG. 1 is a textual flow diagram illustrating an example die processingsequence using a spin plate.

FIG. 2 is a textual flow diagram illustrating an example die processingsequence performed on a dicing tape or device processing film orsurface, according to an embodiment.

FIG. 3 is a graphical flow diagram of the example die processingsequence of FIG. 2 , according to an embodiment.

FIGS. 4A-4E graphically illustrate example steps for transferring diesfrom a dicing sheet to a wafer or a surface, according to an embodiment.

FIGS. 5A-5C illustrate example dicing sheets, with dies removed,according to an embodiment.

FIG. 6 is a textual flow diagram illustrating an example die processingsequence performed on a dicing tape or device processing film orsurface, according to a second embodiment.

FIG. 7 is a textual flow diagram illustrating an example die processingsequence performed on a dicing tape or device processing film orsurface, according to a third embodiment.

FIG. 8 is a graphical flow diagram of the example die processingsequence of FIG. 7 , according to an embodiment.

FIGS. 9A and 9B illustrate example die cleaning systems, according tovarious embodiments.

FIGS. 10A and 10B illustrate example die cleaning systems, according toother embodiments.

DETAILED DESCRIPTION Overview

Various embodiments of techniques and systems for processing integratedcircuit (IC) dies are disclosed. Dies being prepared for intimatesurface bonding (to other dies, to substrates, to another surface, etc.)may be processed with a minimum of handling, to prevent contamination ofthe surfaces or the edges of the dies.

The techniques include processing dies while the dies are on a dicingsheet or other device processing film or surface, according to variousembodiments. For example, the dies can be cleaned, ashed, and activatedwhile on the dicing sheet (eliminating a number of processing steps andopportunities for contamination during processing). The processing canprepare the dies to be bonded in stacked arrangements, for instance.After processing, the dies can be picked directly from the dicing sheetand placed on a prepared die receiving surface (another die, asubstrate, etc.) for bonding to the surface.

In various embodiments, using the techniques disclosed can reduce diefabricating and processing costs and can reduce the complexity offabricating electronic packages that include the dies. Dies to bestacked and bonded using “ZIBOND®” and “Direct Bond Interconnect (DBI®)”techniques, which can be susceptible to particles and contaminants, canparticularly benefit. Whether the manufacturing process includes bondingtwo surfaces using a low temperature covalent bond between twocorresponding semiconductor and/or insulator layers (the process knownas ZIBOND®), or whether the manufacturing process also includes forminginterconnections along with the bonding technique (the process known asDBI®), high levels of flatness and cleanliness are generally desirableacross the bonding surfaces.

The techniques disclosed may also be beneficial to other applicationswhere, for example, the bonding region of the device may compriseflowable mass material such as any form of solderable material forbonding. Minimizing or eliminating particles or dirt between the bondingsurfaces can dramatically improve yield and reliability. In animplementation, large batches of dies can be processed at a time, usinglarge die or wafer carriers such as large dicing sheets, using multipledie or wafer carriers, or the like.

In some embodiments, several process steps can be eliminated, loweringmanufacturing complexity and costs, while improving the overallcleanliness of the dies (e.g., reducing the occurrence of particles,contaminants, residue, etc.). Reduced handling of the dies can alsominimize particle generation.

A flow diagram is shown at FIG. 1 , illustrating an example die ordevice processing sequence 100, using a spin plate to hold the diesduring processing. At blocks 1-4 the process begins with preparing asubstrate, for example a silicon wafer, by applying protective coatingsto one or both sides of the wafer, singulating the wafer into dies(i.e., a first set of dies) on a dicing sheet or the like, exposing thedies and dicing sheet to ultraviolet (UV) radiation and stretching thedicing sheet, and transferring the dies to a spin plate, with the diesface up. At blocks 5-9 the process includes the steps of cleaningorganic layers from the dies, plasma ashing the top surface of the diesto remove any remnant organic residues on the dies, and further cleaningthe dies with deionized water (DI), for example, plasma activating thetop surface of the dies, and re-cleaning the dies.

At block 10, the dies are transferred to a flip plate, to position thedies face down (i.e. the active surfaces (e.g., first surfaces) of thedies are facing downward or toward the flip plate). At block 11, thedies are transferred to a pick and place station. In this arrangement,the dies are picked from their back surface (e.g., the surface oppositethe face, front or first surface, or active surface) and placed facedown on a prepared receiving surface for bonding. To pick up the dies,the picking vacuum tool (for instance) contacts the back or secondsurface of the dies, which is opposite to the surface being bonded.

The receiving surface may include a prepared surface such as asubstrate, another die, a dielectric surface, a polymeric layer, aconductive layer, the surface of an interposer, another package, thesurface of a flat panel, or even the surface of another circuit or asilicon or non-silicon wafer. The material of the dies may be similar ordissimilar to the materials of the receiving substrate. Also, thesurface of the dies may be dissimilar to the surface of the receivingsubstrate.

At block 13, the dies placed on the substrate are thermally treated toenhance the bond between the surface of the dies and the receivingsurface of the substrate. In some embodiments, additional dies may beattached to the back (e.g., second) surface or available surface of thebonded dies. The back surface may additionally have active devicestherein.

At blocks 14-18 the receiving surface, for example the substrate, andthe exposed back surface of the bonded dies are cleaned, plasma ashed,re-cleaned, plasma activated, and cleaned again. At block 19 a secondset of dies (with the top surface previously prepared as described atblocks 1-11) may be attached to the first set of dies (forming a stackeddie arrangement). In an example, the front prepared surface (e.g., firstsurface) of the second dies is attached to the exposed back surface(e.g., second surface) of the first dies. At block 20, the assembly withthe first and second dies is thermally treated to enhance the bonding ofthe stack. For additional dies to be added to the stacked diearrangement (e.g., third or more dies), the process is looped back toblock 14, and continues until the desired quantity of dies has beenadded to each stack.

In various examples, the manufacturing process as described can use atleast or approximately 13+7(n−1); n>0 steps to complete (where n=thedesired quantity of dies in the stack).

In some cases, in spite of the numerous cleaning steps included in theprocess, the dies are left with some contamination or particles on oneor more surfaces of the dies. For instance, a top or front surface of adie may be cleaned free of contamination while a bottom or back surfaceof the die may be left with particles or contamination. Additionally,handling the dies during the multiple processing steps can add particlesor contaminants to the dies. For example, tools used during handling cantransfer contaminants to the dies. The location of the particles ordefects on the dies can determine whether the particles or defects canbe potentially problematic for the stacked arrangement. For instance,some particles and defects can cause poor bonding between stacked dies,and the like. In another example, the device flipping step can be asource of contamination or defects, because the cleaned top surface ofthe device comes in contact with another surface after the flippingoperation.

Example Implementations

FIG. 2 is a flow diagram illustrating an example die processing sequence200, where the dies are processed on a carrier such as a dicing tape(“dicing sheet”) or other processing sheet, according to an embodiment.FIG. 3 shows a graphical flow diagram representation of the process 200,according to an example implementation. The process 200 is discussedwith reference to FIG. 2 and FIG. 3 , however, “blocks” referred to inthis discussion refer to the numbered blocks at FIG. 2 , unlessspecified otherwise.

At block 1, a wafer 302 is processed, including adding one or moreprotective layers or coatings 304 to one or both surfaces of the wafer302 (block 2). The protective layers 304 may include photoresists, orsimilar protectants. The wafer 302 is transferred to a dicing sheet 306and temporarily fixed to the dicing sheet 306 with an adhesive 308. Atblock 3, the wafer 302 is singulated into dies 310 while on the dicingsheet 306.

At block 4, the dies 310 are cleaned to remove particles, including theedges of the dies 310, while attached to the dicing sheet 306. Thecleaning can be performed mechanically and/or chemically. For example,the dies 310 may bombarded with fine CO2 particles and/or exposed to abrush cleaning step which may be ultrasonically or megasonicallyenhanced. The brush 312 (as shown in FIG. 3 ) may rotate in anydirection or otherwise move relative to the die 310 surface. The die 310may additionally or alternatively be exposed to a wet etch, water pick,and so forth. At block 5, the dicing sheet 306 may be slightly stretchedto create spaces between dies 310, to accommodate cleaning the edges ofthe dies 310. The dies 310 on the dicing sheet 306 may be exposed toultraviolet (UV) radiation to break down the resist 304 and/or adhesive308 layers. The dicing sheet 306 may be further stretched if needed toprepare the dies 310 for removal from the dicing sheet 306.

At block 6, remaining residue of the resist layer 304 is cleaned off ofthe exposed surface (e.g., first surface) of the dies 310, while thedies 310 are on the dicing sheet 306. A cleaning solution may be used,as well as other chemical and/or mechanical cleaning techniques such asthose described herein. Additionally, the first (e.g., exposed) surfaceof the dies 310 is plasma ashed (e.g., oxygen ashing) while the dies 310remain on the dicing sheet 306, to remove any unwanted organic residue.

At block 7, the first surface of the dies 310 is cleaned again, using awet cleaning technique (e.g., deionized water, cleaning solution, etc.),which may include megasonic scrubbing, mechanical brush scrubbing, oragitation, or other suitable cleaning techniques. For example, in someinstances, after the ashing step, additional cleaning may be performedby a wet cleaning and/or by CO2 particle stream, or a rotary brush,water pick, or megasonic assisted wet cleaning technique, orcombinations thereof.

At block 8, the first surface of the dies 310 is plasma activated (e.g.,nitrogen plasma, etc.) to create or enhance bonding for stacking thedies 310. At block 9, the activated dies 310 are cleaned using a wetcleaning technique (e.g., deionized water, hot deionized water, watervapor, or a high pH cleaning solution, etc.), that may be enhanced withmegasonics, or a combination of cleaning techniques described above, orthe like.

At block 10, the dies 310 (e.g., known good dies) 310 are transferredfrom the dicing sheet 306 to the receiving surface 314 (a prepared die,a substrate, etc.) for bonding to the receiving surface 314. In somecases, the various cleaning and surface activating processes that arediscussed above may be performed on the exposed surface of the dies 310and/or the receiving surface 314.

In various embodiments, the dies 310 are transferred from the dicingsheet 306 using a “punch” technique (as illustrated in FIGS. 4 and 5 ).The punch technique allows the dies 310 (e.g., known good dies) to betransferred without contaminating a surface or an edge of the dies 310.Also, the punch technique allows the dies 310 (e.g., known good dies) tobe bonded to the bonding surface 314 “face down,” that is with the firstsurface of the dies 310 facing the receiving surface 314, using a DBIhybrid bonding technique, solder bumping, or the like.

In one example, as shown in FIGS. 4(A), 5(A), and 5(B), the stretcheddicing sheet 306 is held by a grip ring 402, or a frame, or the like.The dies 310 on the dicing sheet 306 are separated by gaps 404 (about 2um-200 um wide), which may be due at least in part to the stretching. Asshown at FIGS. 4(B) and 4(C), the dicing sheet 306 may be perforatedalong the gaps 404 between dies 310 using one or more of various tools406, such as a dicing blade, hot knife, an optical knife (laserablation), etc. In an embodiment, the perforating allows the dies 310(e.g., known good dies) to be punched from the dicing sheet 306individually, leaving the other dies 310 in place on the dicing sheet306. A vacuum tool 408 or the like (i.e., “pick up head”) can be used topunch individual dies 310 from the perforated dicing sheet 306 (as shownat FIG. 4(B)), from the back of the dicing sheet 306, for example. Thevacuum tool 408 is able to transfer the dies 310 (e.g., known good dies)from the surface of the dicing tape 306 opposite the die 310, with aportion of the dicing tape 306 (or processing sheet) in place betweenthe tool 408 and the die 310. Thus, the die 310 (e.g., known good die)arrives at the bonding surface 314 without the vacuum tool 408contaminating the to-be-bonded surface or an edge of the die 310. Theportion of the tape 306 that remains attached to the back surface of thedie 310 (e.g., known good die) thereby protects the die 310 from beingcontaminated by contact with the tool 408.

FIG. 4(D) shows a profile view of the dicing sheet 306 with a die 310removed. There is a hole 410 in the dicing sheet 306, since a portion ofthe dicing sheet 306 is removed with the die 310. (This is further shownat FIGS. 5(A)-5(C)). FIG. 4(E) shows a number of dies 310 placed on asubstrate 314 for bonding.

In another embodiment, the device pick up head 408 (e.g., vacuum tool),picks the die 310 (e.g., known good die) from the backside of the die310 (e.g., known good die) through the dicing sheet 306, assimultaneously a corresponding tool ablates the dicing sheet 306 aroundthe perimeter of the die 310 with a laser source (or the like). In someapplications, during the die 310 pick up by the vacuum tool 408 from theback side, a heated knife 406 edge may be used to melt the dicing sheet306 around the die 310 to fully separate the die 310 from the dicingsheet 306. Inert gas may be applied to the surface of the dies 310 toprevent smoke or other contaminants from the device separation step fromcontaminating the cleaned surface of the dies 310. In other embodiments,vacuum may be used in place of the inert gas, while in furtherembodiments, both inert gas and vacuum are used to protect the surfaceof the dies 310 during the device separation process.

In various implementations, the cleaned, exposed surface of the die 310is not touched by any another surface or material except the surface ofthe receiving substrate 314. This is in contrast to some priortechniques, wherein the cleaned surface of the die 310 (e.g., known gooddie) generally contacts some portion of the receiving flip plate. Inother common techniques, a vacuum pickup device 408, for example, maypick up the clean dies 310 (e.g., known good dies) by touching a portionof the cleaned die 310 surface, which can result in contaminating thetouched surface.

Referring back to FIGS. 2 and 3 , at block 11, the wafer or substrate314 with the newly stacked dies 310 is thermally treated (e.g., to50-150° F.) to strengthen the bonding of the dies 310 to the substrate314. At block 12, the current exposed surface (“back surface” or “secondsurface”) of the dies 310 and the substrate 314 are prepared by chemicaland/or mechanical cleaning techniques (e.g., surfactant, non-PVA rotarybrush, megasonics, etc.). This removes any remaining adhesive 308,dicing sheet 306, protective layers 304, or other residue from the backsurface of the dies 310. At block 13, the back surface of the dies 310is plasma activated to prepare for further bonding.

At block 14, additional prepared dies 316 are separated by thetechniques disclosed herein and disposed with the first surface “facedown” (e.g., active side down, prepared side down, etc.) on the preparedback (e.g., second) surface of the dies 310 previously placed on thesubstrate 314, for example. The newly added dies 316 are thermallytreated (e.g., block 11) to strengthen the bonds to the dies 310. Foradditional dies 316 to be added to the stacked die arrangement (e.g.,third or more dies), the process is looped back to block 12, andcontinues until the desired quantity of dies 310, 316 has been added toeach stack.

In various examples, the manufacturing process as described can useapproximately 11+2(n−1); n>0 steps to complete (where n=the desiredquantity of dies 310, 316 in the stack). This represents a significantreduction in manufacturing steps when compared to the process describedwith respect to FIG. 1 : (13+7(n−1)). Not only is manufacturing cost andcomplexity reduced by reducing process steps, but opportunities tocontaminate the dies 310 are also reduced, resulting in better qualityand higher throughput with lower cost. The reduced processing stepstranslate to a cost savings per die 310, and the elimination of a spinplate (or like processing component) translates to further manufacturingcost savings. For example, approximately 50 to 100 dies 310 can beprocessed at a time using spin plates, and approximately 200 to 10,000dies 310 or more can be processed at a time using a dicing sheet 306process as described.

A second example embodiment 600 for processing dies 310 on a dicingsheet 306 is shown at FIG. 6 . The example embodiment 600 illustratesthat some of the process steps may be performed in a different order,including reducing process steps as well. For example, at blocks 1-3,the wafer 302 is processed with protective coatings 304, singulated intodies 310 on the dicing sheet 306 and cleaned on the dicing sheet 306 aspreviously described. Optionally, the dicing sheet 306 may be stretchedsome to accommodate cleaning between the dies 310, and/or the dies 310may be exposed to UV light to break down the resists 304 and adhesives308. At block 4, the first surface of the dies 310 is plasma ashed(e.g., oxygen ashing) while the dies 310 remain on the dicing sheet 306,to remove any unwanted organic residue (or other contaminants) from thefirst surface.

At block 5, the ashed surface of the dies 310 is cleaned using a wetcleaning technique (e.g., deionized water, cleaning solution, etc.) asdescribed above, which may include megasonics, or the like. At block 6,the first surface of the dies 310 is plasma activated (e.g., nitrogenplasma, etc.) to create or enhance bonding for stacking the dies 310. Atblock 7, the activated dies 310 are exposed to UV light and the dicingsheet 306 is partially stretched. At block 8, the activated dies 310 arecleaned using a wet cleaning technique (e.g., deionized water, hotdeionized water, water vapor, or a high pH cleaning solution, etc), thatmay be enhanced with megasomcs, or a combination of cleaning techniquesdescribed above, or the like.

At block 9, the dies 310 are transferred from the dicing sheet 306 tothe bonding surface 314, and bonded with the first surface “face down”using a DBI hybrid bonding technique, solder bumping, or the like, forexample. In the various embodiments, the dies 310 are transferred fromthe dicing sheet 306 using the “punch” technique described above(including perforating the dicing sheet 306 and transferring the dies310 using a vacuum tool 408, or the like, while a portion of the dicingsheet 306 remains on the dies 310 to protect the dies 310 fromcontamination by the vacuum tool 408). At block 10, the dies 310 andsubstrate 314 are thermally treated (e.g., to 50-1500 F) to strengthenthe bond of the dies 310 to the substrate 314. At block 11, the exposedsurface (“back surface” or “second surface”) of the dies 310 and thesubstrate 314 are cleaned using chemical and/or mechanical cleaningtechniques (e.g., surfactant, non-PVA rotary brush 312, megasonics,etc.). This removes any remaining adhesive 308 or other residue from theback surface of the dies 310. At block 12, the back surface of the dies310 is plasma activated to prepare for further bonding.

At block 13, additional dies 316 may be punched from the perforateddicing sheet 306 (as described above) and placed “face down” on the back(e.g., exposed) surface of the dies 310 previously placed on thesubstrate 314, for example. The newly added dies 316 are thermallytreated (e.g., block 10) to strengthen the bonds. For additional dies310, 316 to be added to the stacked die arrangement (e.g., third or moredies), the process is looped back to block 11, and continues until thedesired quantity of dies 310, 316 has been added to each stack.

In various examples, the manufacturing process as described can useapproximately 10+2(n−1); n>0 steps to complete (where n=the desiredquantity of dies 310, 316 in the stack), resulting in further reductionof steps, complexity, and cost.

FIG. 7 is a flow diagram illustrating another example die 310 processingsequence 700 performed on a dicing tape 306, according to a thirdembodiment. FIG. 8 is a graphical representation of the example dieprocessing sequence 700 of FIG. 7 , according to an exampleimplementation. In the example embodiment of FIGS. 7 and 8 , the plasmaashing step (i.e., block 4 of FIG. 6 ) is eliminated, reducing theprocess steps.

At blocks 1-3, the wafer 302 is processed with protective coatings 304,singulated into dies 310 on the dicing sheet 306 and cleaned on thedicing sheet 306 as previously described. Optionally, the dicing sheet306 may be stretched some to accommodate cleaning between the dies 310,and/or the dies 310 may be exposed to UV light to break down the resists304 and adhesives 308. At block 4, the first surface of the dies 310 isplasma activated (e.g., nitrogen plasma, etc.) to create or enhancebonding for stacking the dies 310. At block 5, the activated dies 310are cleaned using a wet cleaning technique (e.g., deionized water, ahigh ph cleaning solution, etc), which may include megasonic scrubbing,agitation, or other suitable cleaning techniques. At block 6, theactivated dies 310 are exposed to UV light and the dicing sheet 306 ispartially stretched.

At block 7, the dies 310 are transferred from the dicing sheet 306 tothe bonding surface 314, and bonded with the first surface “face down”using a DBI hybrid bonding technique, solder bumping, or the like. Inthe various embodiments, the dies 310 are transferred from the dicingsheet 306 using the “punch” technique described above (includingperforating the dicing sheet 306 and transferring the dies 310 using avacuum tool 408, or the like, while a portion of the dicing sheet 306remains on the dies 310 to protect the dies 310 from contamination bythe vacuum tool 408). At block 8, the dies 310 and substrate 314 arethermally treated (e.g., to 50-150° F.) to strengthen the bond of thedies 310 to the substrate 314. At block 9, the exposed surface (“backsurface” or “second surface”) of the dies 310 and the substrate 314 arecleaned using chemical and/or mechanical cleaning techniques (e.g.,surfactant, methanol, non-PVA rotary brush 312, megasonics, etc.). Thisremoves any remaining adhesive 308 or other residue from the backsurface of the dies 310. At block 10, the back surface of the dies 310is plasma activated to prepare for further bonding.

At block 11, additional dies 316 may be punched from the perforateddicing sheet 306 and placed “face down” (e.g., prepared side down) onthe back surface (e.g., exposed surface) of the dies 310 previouslyplaced on the substrate 314, for example. The newly added dies 316 arethermally treated (e.g., block 8) to strengthen the bonds. Foradditional dies 310, 316 to be added to the stacked die arrangement(e.g., third or more dies 310, 316), the process is looped back to block9, and continues until the desired quantity of dies 310, 316 has beenadded to each stack.

In various examples, the manufacturing process as described can useapproximately 8+2(n−1); n>0 steps to complete (where n=the desiredquantity of dies 310, 316 in the stack), resulting in further reductionof steps, complexity, and cost. After the device stacking steps, thestacked dies 310 and the receiving surface 314 may be further treated toa subsequent higher temperature. The treating temperature may range from80 to 3 70° C. for times ranging between 15 minutes to up to 5 hours orlonger. The lower the treatment temperature, the longer the treatmenttimes.

In one embodiment of the process 700, the wafer 302 to beprocessed/diced may include interconnects such as solder bumps or otherreflowable joining materials (not shown), or the like, on the exposed orfirst surface. In the embodiment, the reflowable interconnect joiningstructure or structures are often disposed face up on the dicing sheet306 or processing sheet, in a manner that the reflowable features do notdirectly contact the adhesive layer 308 of the dicing sheet 306. Thewafer 302 may be processed with protective coatings 304 overlaying thereflowable interconnect structures. The wafer 302 is singulated intodies 310 while on the dicing sheet 306, and cleaned while on the dicingsheet 306 as previously described with respect to blocks 1-3 above.Optionally, the dicing sheet 306 may be stretched some to accommodatecleaning between the dies 310 and the edges of the dies 310, and/or thedies 310 may be exposed to UV light to break down the resists 304 andadhesives 308.

At block 4, the first surface (e.g., exposed surface) of the dies 310may be cleaned with plasma cleaning methods (e.g., oxygen ashing etc.).At block 5, the dies 310 on the dicing sheet 306 may be further cleanedusing a wet cleaning technique as described above (e.g., deionizedwater, a high ph cleaning solution, etc.), which may include megasonics,agitation, or the like, if desired. At block 6, the cleaned dies 310 andthe dicing sheet 306 may be exposed to UV light and the dicing sheet 306may be further stretched.

At block 7, the dies 310 are transferred from the dicing sheet 306 tothe receiving surface 314, and bonded with the first surface “face down”(e.g., prepared surface down) using the techniques described herein. Insome embodiments, the receiving substrate 314 may comprise a polymericlayer, a no-fill underfill, or portions of an adhesive sheet, forexample. In the various embodiments, the dies 310 are transferred fromthe dicing sheet 306 using the “punch” technique described above(including perforating the dicing sheet 306 and transferring the dies310 using a vacuum tool 408, or the like, while a portion of the dicingsheet 306 remains on each of the dies 310 to protect the dies 310 fromcontamination by the vacuum tool 408).

At block 8, the dies 310 and substrate 314 may be thermally treated toelectrically couple the dies 310 to the receiving substrate 314. In someapplications, underfill materials may be formed around the bonded device310 to further mechanically couple the device 310 to the substrate 314receiving surface. At block 9, the exposed surface of the transferreddies 310 and the substrate 314 are cleaned using chemical and/ormechanical cleaning techniques (e.g., surfactant, methanol, non-PVArotary brush 312, megasonics, etc.). This removes any remaining adhesive308 or other residue from the back surface of the dies 310. At block 10,the exposed surface of the transferred dies 310 is plasma activated toprepare for further bonding. In some applications, the bonded devices310 may be cleaned before the thermal processing to electrically couplethe dies 310 to the receiving substrate 314.

As discussed above, at various processing steps or stages, dies 310, 316and/or substrates 314 are cleaned using chemical and/or mechanicalcleaning techniques (e.g., surfactant, methanol, non-PVA rotary brush312, megasonics, etc.). FIGS. 9A and 9B illustrate example die cleaningsystems, which may be used for this purpose, according to variousembodiments. The cleaning processes and systems are described withreference to dies 310, or the receiving surface of the substrate 314,but it is to be understood that the processes and systems are applicableto dies 310, 316 and substrates 314, as well as dielectric surfaces,polymeric layers, conductive layers, interposers, packages, panels,circuits, silicon or non-silicon wafers, and the like.

Referring to FIG. 9A, in an example cleaning sequence, the object(s) tobe cleaned (for example, dies 310 or a carrier, etc.) are loaded ontoprocessing equipment 902 (such as a turntable or spin-plate as shown)for cleaning and/or other processing. The cleaning process includesapplying proximity megasonic energy to a cleaning fluid, via a megasonictransducer 904, while the dies 310 may be rotated on the turntable 902.The transducer 904 may be scanned back and forth while the dies 310rotate to improve even application of sonic energy to the dies 310. Thesonic energy helps to loosen particles that may be otherwise difficultto remove from the die 310 surfaces.

Referring to FIG. 9B, the transducer 904 is then removed, and thesurface of the dies 310 may be brushed clean with a brush 906. The brush906 may be scanned back and forth while the turntable 902 rotates, forexample. If this cleaning process is not successful in removingsufficient particles, the process may be repeated as desired. The dies310 are rinsed and dried when the cleaning process is complete. However,in some cases this can require multiple cycles, and still may beinsufficient to clean all residues from the dies 310.

Referring to FIGS. 10A and 10B, techniques and systems provide improvedcleaning of die/wafer/substrate surfaces in a single process. FIGS. 10Aand 10B illustrate example die 310 cleaning systems 1000, according tovarious embodiments. An integrated megasonic brush system 1000 isdisclosed that includes a megasonic transducer 1002 and one or morebrush heads 1004.

In a first embodiment, as shown at FIG. 10A, the integrated megasonicbrush system 1000 is placed in proximity to the dies 310 on theturntable 902 (or other process surface). The integrated megasonic brushsystem 1000 is located so that the transducer 1002 is at an optimaldistance from the die 310 surfaces, and so that the brush(es) 1004 havea desired contact pressure on the die 310 surfaces. A cleaning fluid isapplied to the die 310 surfaces, for instance. While the transducer 1002applies sonic energy to the die 310 surfaces via the cleaning fluid, thebrush(es) 1004 simultaneously brush particles from the die 310 surfaces.In various implementations, the dies 310 are rotated on the turntable902 and/or the integrated megasonic brush system 1000 is scanned backand forth for even cleaning.

In an implementation, a fluid height sensor 1006 assists in controllingthe amount of cleaning fluid applied to the die 310 surfaces, sending asignal to a cleaning fluid reservoir, for example. In theimplementation, the fluid height sensor 1006 is positioned above thedie(s) 310 and is arranged to detect a height of a fluid over the die(s)310. The fluid height sensor 1006 is arranged to send at least a firstsignal to a fluid source when the height of the fluid is less than afirst predetermined amount and a second signal to the fluid source whenthe height of the fluid is greater than a second predetermined amount.The combination of megasonics and brushing in a single system andprocess allows more thorough cleaning in the single process, which caneliminate repeated cleaning iterations.

In a second embodiment, as shown at FIG. 10B, the one or more brushes1004 may be rotated via a rotary unit 1008 while brushing the surfacesof the dies 310. For example, the brush(es) 1004 may be rotated (e.g.,the rotary unit 1008 may rotate the brushes 1004) using hydraulics, orany other suitable means (pneumatic, electric, mechanical, etc.),delivered via a conduit 1010, cable, or the like. The additionalrotation of the brush(es) 1004 can assist in removing difficultparticles from the surfaces of the dies 310 in a single cleaning systemand process.

The techniques and systems can prepare the dies 310 to be bonded instacked arrangements, by providing cleaner bonding surfaces with fewerprocess steps. After processing and cleaning, the dies 310 can be pickedand placed on a die receiving surface 314 (another die, a substrate,etc.) for bonding to the receiving surface 314, as described above. Dies310 to be stacked and bonded using “Zibond®” and “Direct BondInterconnect (DBI®)” techniques, which can be susceptible to particlesand contaminants, can particularly benefit. The techniques disclosed mayalso be beneficial to other applications where, for example, the bondingregion of the die 310 may include flowable mass material such as anyform of solderable material for bonding. Minimizing or eliminatingparticles or dirt between the bonding surfaces may dramatically improveyield and reliability. Additional benefits include improved efficiencyof the cleaning process and the cleaning equipment, more simplifiedprocess steps and process equipment, a significant reduction in cleaningcycle time, and the like.

Examples of cleaning cycles wherein the disclosed techniques and systemsmay be employed include: cleaning the dies 310 after a CMP process,after etching, or the like, cleaning organic (or inorganic)manufacturing and processing layers from the dies 310, cleaning the dies310 with deionized water (DI), basic or acidic solutions, or slightlybasic or slightly acidic formularies, solvents, or their variouscombinations following plasma ashing the surface of the dies 310,re-cleaning the dies 310 after plasma activating the surface of the dies310, and so forth. In various embodiments, the ashing step may beomitted and the dies 310 cleaned in the equipment described in FIGS. 10Aand 10B, for example. In one embodiment, for example, the protectivelayer 304 may be cleaned off using the equipment described in FIGS. 10Aand 10B using applied sonic energy and mechanical action of the brush1004 to remove the protective layer 304 with a suitable solvent. Toprevent cross contamination of tools and devices, in the subsequentsteps the cleaned dies 310 may be transferred to another cleaningstation of the type described with reference to FIGS. 10A and 10B foradditional cleaning, for example, to eliminate the ashing step or afterthe activation of the dies 310.

As described in the various preceding paragraphs, the singulated dies310 may be processed on a carrier 306. In some embodiments, known gooddies 310 are removed from the carrier 306 with at least portion of thecarrier 306 attached to the second surface of the known good dies 310. Afirst known good die 310 is attached to a prepared surface of thesubstrate 314, at the first surface of the first known good die 310.Similarly, a second surface of the first known good die 310 may becleaned (including cleaning off the portion of the carrier 306) andprepared for bonding of another known good die 316. In practice, thebacksides (e.g., second sides) of any of the bonded dies 310, 316 may beprepared, and additional dies 310, 316 may be bonded thereon. Anyadditional dies 310, 316 may be bonded to the previously bonded dies310, 316 as desired. In various embodiments, the stacked bonded dies(310, 316, etc.) may range from 1 to 200 dies 310,316 and preferablybetween 1 to 100 dies 310, 316 and still preferably between 1 to 20known good dies 310, 316.

The techniques described can result in better device and packagereliability, higher performance, and improved profit margin for ZiBond®and DBI® manufactured devices, and the like. Other advantages of thedisclosed techniques will also be apparent to those having skill in theart.

CONCLUSION

Although the implementations of the disclosure have been described inlanguage specific to structural features and/or methodological acts, itis to be understood that the implementations are not necessarily limitedto the specific features or acts described. Rather, the specificfeatures and acts are disclosed as representative forms of implementingexample devices and techniques.

Each claim of this document constitutes a separate embodiment, andembodiments that combine different claims and/or different embodimentsare within the scope of the disclosure and will be apparent to those ofordinary skill in the art upon reviewing this disclosure.

1. (canceled)
 2. A method of forming a microelectronic assembly, themethod comprising: attaching a wafer to a carrier, wherein the wafercomprises first and second bonding surfaces and wherein attaching thewafer to the carrier comprises attaching the second bonding surface tothe carrier; singulating the wafer into a plurality of die components,wherein the plurality of die components comprises a known good die andwherein the known good die comprises a portion of the first bondingsurface and a portion of the second bonding surface; while the pluralityof die components are attached to the carrier, cleaning the plurality ofdie components; removing the known good die from the carrier; directlybonding the portion of the first bonding surface to a surface of asubstrate; and cleaning the portion of the second bonding surface whilethe known good die is directly bonded to the substrate.
 3. The method ofclaim 2, further comprising: before singulating the wafer into theplurality of die components, forming a protective layer on the firstbonding surface.
 4. The method of claim 3, further comprising: beforedirectly bonding the portion of the first bonding surface to the surfaceof the substrate, cleaning the protective layer from the portion of thefirst bonding surface.
 5. The method of claim 2, wherein the carriercomprises dicing tape.
 6. The method of claim 2, wherein, after removingthe known good die from the carrier, the portion of the second bondingsurface comprises residue and wherein cleaning the portion of the secondbonding surface comprises cleaning the residue from the portion of thesecond bonding surface.
 7. The method of claim 6, wherein the residuecomprises one or more of organic residue or a portion of the carrier. 8.The method of claim 2, wherein cleaning the portion of the secondbonding surface comprises cleaning the portion of the second bondingsurface with one or more of a CMP process, a brush cleaning process, ora megasonic cleaning process.
 9. The method of claim 2, wherein theknown good die comprises a first known good die, the method furthercomprising: after cleaning the portion of the second bonding surfacewhile the first known good die is directly bonded to the substrate,directly bonding a second known good die to the portion of the secondbonding surface of the first known good die.
 10. The method of claim 9,further comprising: before directly bonding the second known good die tothe portion of the second bonding surface of the first known good die,activating the portion of the second bonding surface of the first knowngood die.
 11. The method of claim 9, further comprising: before directlybonding the second known good die to the portion of the second bondingsurface of the first known good die, thermally treating the first knowngood die and the substrate.
 12. A method of forming a microelectronicassembly, the method comprising: attaching a wafer to a carrier, whereinthe wafer comprises first and second bonding surfaces and whereinattaching the wafer to the carrier comprises attaching the secondbonding surface to the carrier; singulating the wafer into a pluralityof die components, wherein the plurality of die components comprises aknown good die and wherein the known good die comprises a portion of thefirst bonding surface and a portion of the second bonding surface;cleaning the plurality of die components on the carrier; after cleaningthe plurality of die components, removing the known good die from thecarrier; directly bonding the portion of the first bonding surface ofthe known good die to a surface of a substrate; cleaning the portion ofthe second bonding surface of the known good die; and directly bonding asecond die to the portion of the second bonding surface.
 13. The methodof claim 12, wherein the known good die comprises a first known good dieand wherein the second die comprises a second known good die.
 14. Themethod of claim 12, wherein cleaning the portion of the second bondingsurface of the known good die comprises cleaning residue or organicresidue from the portion of the second bonding surface of the known gooddie.
 15. The method of claim 12, wherein cleaning the portion of thesecond bonding surface comprises cleaning the portion of the secondbonding surface with a CMP process, a brush cleaning process, or amegasonic cleaning process.
 16. The method of claim 12, furthercomprising: before directly bonding the second die to the portion of thesecond bonding surface, activating the portion of the second bondingsurface.
 17. The method of claim 12, wherein the second die comprises athird bonding surface and wherein directly bonding a second die to theportion of the second bonding surface comprises directly bonding thethird bonding surface to the portion of the second bonding surface, themethod further comprising: before directly bonding the third bondingsurface to the portion of the second bonding surface, activating thethird bonding surface.
 18. The method of claim 12, further comprising:after directly bonding the second die to the portion of the secondbonding surface, thermally treating the known good die, the second die,and the substrate.
 19. A method of forming a microelectronic assembly,the method comprising: attaching a wafer to a carrier, wherein the wafercomprises first and second bonding surfaces and wherein attaching thewafer to the carrier comprises attaching the second bonding surface tothe carrier; applying a protective layer to the first bonding surface;singulating the wafer into a plurality of die components, wherein theplurality of die components comprises a known good die, wherein theknown good die comprises a portion of the first bonding and portion ofthe second bonding surface, and wherein the portion of the first bondingsurface comprises a portion of the protective layer; cleaning the knowngood die, wherein cleaning the known good die comprises removing theportion of the protective layer from the portion of the first bondingsurface; removing the known good die from the carrier; directly bondingthe portion of the first bonding surface to a surface of a substrate;and after directly bonding the portion of the first bonding surface tothe surface of the substrate, cleaning the portion of the second bondingsurface of the known good die.
 20. The method of claim 19, whereincleaning the portion of the second bonding surface comprises cleaningthe portion of the second bonding surface with one or more of a CMPprocess, a brush cleaning process, or a megasonic cleaning process. 21.The method of claim 19, wherein the known good die comprises a firstknown good die, the method further comprising: after cleaning theportion of the second bonding surface while the first known good die isdirectly bonded to the substrate, directly bonding a second known gooddie to the portion of the second bonding surface of the first known gooddie.